Quit all programs, then try to go to Disk Utility > First Aid to repair a storage device in Disk Utility
Also, you can try to open the file, and save it as copy, before saving, you can rename the copy. Or copy the all the content to a newly created blank workbook.
In order to narrow down the cause to determine whether it is a problem with Excel or your Mac, please provide the following information:
1. Is the file saved locally or in your OneDrive?
2. Does the problem occur to only one file or ALL files?
3. Can you rename other files in the same location, especially those not generated by Excel/ Office apps?
4. The version number of your Mac OS, for example, Catalina 10.15.3
5. The version number of your Excel, for example, version 16.34 (20020900)
6. A screenshot of the error message, sometimes the description of the error message points to the cause of the problem.
Looking forward to your feedback and I’ll continue to help you.